Method for validating radiographic inspection of projectile

ABSTRACT

This invention provides a method used for radiographic inspection of  matel within a container, where the container is a dense material and the contents to be radiographically inspected are of a less dense material.

GOVERNMENTAL INTEREST

The invention described herein may be made, used or licensed by or forthe Government for Governmental purposes without the payment to theinventors of any royalties thereon or therefor.

BACKGROUND

In early 1990, there was an increase in the failure of M825A1 projectilebursters to function during projectile firings. This was subsequentlydetermined to be due to the presence of voids or cracks with the A-5explosive within the burster tube. Each such failure results in the lossof hundreds of dollars of U.S. Army funds.

Even though it is required that each projectile burster be x-rayed todetect voids, cracks or foreign materials with the explosive, thesex-rays are not consistently reliable. The problem in x-raying theprojectile burster contents is that the x-ray must pass through thedense metal burster tube and accurately x-ray the less dense explosivematerial. Prior to the present invention there was no way to ensure thatan absence of indicators on the developed film indicated explosiveconsolidation rather than a failure of the equipment to detect cracks,voids or foreign material through the metal tube walls caused bymis-calibration or mis-focus of the x-ray machine.

SUMMARY

The present invention has provided a method which ensures that eachx-ray machine used to x-ray projectile bursters will be properly focusedand calibrated. The method of the present invention involves x-raying aburster tube which contains a explosive simulant having a predetermineddensity and size. The x-ray film is evaluated to determine whether thex-ray machine's calibration and focus need to be adjusted.

Additionally, the burster tube x-ray film from a properly calibrated andfocused x-ray machine can be used as a visual comparison for assessingthe size of gaps/voids in a projectile burster containing an actualexplosive.

DETAILED DESCRIPTION

This invention provides a method by which to validate the calibrationand focus of an x-ray machine used for the radiographic inspection ofprojectile bursters. One aspect of the present invention provides forthe use of a penetrometer, in the form of a metal burster tube whichcontains an explosive simulant in the form of pellets which have a knowndensity and dimensions. The exact dimensions of the explosive simulantpellets allow for gaps/voids of a predetermined widths and depthsbetween the pellets. An x-ray photograph of the explosive simulantcontaining burster is taken, and the quality and visibility of the gapsor voids on the x-ray film of the explosive simulant containing bursterare used to evaluate and adjust the calibration and focus of the x-raymachine. Preferably, the density of the explosive-simulating pellets issimilar to that of the explosive which is used in the projectileburster. The dimensions of the pellets allow for gaps between thepellets having a width of 0.01 inch and depth of 0.05 inch.

Another aspect of the present invention provides a method for inspectingprojectile bursters using a calibrated and focused x-ray machine. X-raysare taken of a projectile burster containing explosive pellets simulantin place of the regular explosive and also of a projectile burstercontaining explosive. Then the two x-ray films are visually compared.Excessive gaps or voids in the explosive contained within the projectileburster may result in the failure of the projectile burster to explode.Therefore inspection of the projectile bursters by this radiographicmethod provides a criteria by which x-rays of projectile bursters can beevaluated. The criteria used to judge the acceptance or rejection of theprojectile burster are as follows: Longitudinal and traverse gaps orvoids of less than 0.010 inch wide are permitted. A single longitudinalgap or void may extend a maximum of 8 inches in length. However, theaggregate length of cracks in any one projectile burster shall notexceed 12 inches.

Another embodiment of the present invention provides for the validationof the radiographic inspection of a M825A1 projectile burster, whichcontains an A-5 explosive. The simulant pellets contained within thepenetrometer are made of inert plastic, preferably a polyacetyl polymerwhich has a density of 1.41-1.43 close to that of the A-5 explosive. Thepellets have exact dimensions which provide for a gap or void betweenthe pellets which is 0.01 inch wide and 0.05 inch deep.

The present invention is not limited to the inspection of projectilebursters. The methodology of placing a material of a known densitywithin a container, can be adapted by one skilled in the art for thevalidation of radiographic instruments used to x-ray through any densematerial to actually x-ray inspect the less dense material containedwithin.

We claim:
 1. A method of inspecting projectile bursters using a properlycalibrated and focused machine comprising:x-raying a projectile burstercontaining explosive simulant pellets, x-raying a projectile burstercontaining explosive which is to be inspected, comparing the x-ray filmsof the projectile burster to that of the burster containing theexplosive simulant pellets, and evaluating the x-ray film of theprojectile burster based on criteria specific to the burster andexplosive it contains.
 2. A method as in claim 1, wherein saidprojectile burster to be inspected is a M825A1.
 3. A method as in claim2, wherein said projectile burster contains an A-5 explosive.
 4. Amethod as in claim 3, wherein said criteria are:(i) longitudinal andtraverse gaps or voids of less than 0.010 inch wide are permitted, (ii)a single longitudinal gap or void may extend a maximum of 8 inches inlength, and (iii) an aggregate length of gaps or voids in any one ofsaid projectile burster cannot exceed 12 inches.
 5. A method ofinspecting x-ray film of a material within a container to determine theacceptibility or unacceptibility of gaps or voids in the material usinga properly calibrated and focused machine comprising:x-raying a testcontainer containing pellets having a predetermined density andpredetermined size, x-raying a container containing material which is tobe inspected, comparing the x-ray films of the material to be inspectedto that of the test container, and evaluating the x-ray film of thematerial being inspected based upon criteria specific to the containerand material it contains.